import java.util.List;

class Solution2 {
    public  ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        return difs(list1,list2);
    }

    public ListNode difs(ListNode l1, ListNode l2) {
        if(l1 == null) return l2;
        if(l2 == null) return l1;
        if(l1.val > l2.val) {
            l2.next = difs(l1,l2.next);
            return l2;
        }else {
            l1.next = difs(l1.next,l2);
            return l1;
        }
    }

}